Like MajecticFae said, what is politically can be considered relative. However politically correct refers mainly to views of some form of a majority. Otherwise it would be in the realm personal views.
And I don’t see SSC as being part of a “crowd” or specific group other than the BDSM community as a whole. Some people may take it further to mean other things but I doubt anyone here would disagree with its basic principles. Otherwise they would probably be in a rape forum rather than a BDSM forum. Safe is relative to a person’s individual values and motivations. However sane and consensual is pretty straight forward. Don’t lose yourself in the situation and, well, both people have to be willing. Beating your slave while on acid or kidnapping are generally a bad things.
And RACK is another good acronym as there is always risk in everything and we may as well acknowledge that risk. Whether it’s during a vanilla activity or other. However I’m not going to assume you believe sane and consensual are unimportant.
However, back to the political correctness situation. Perhaps I don’t see many things as really being politically incorrect in this lifestyle because I am fairly open about the various things that go on and support people’s right to carry do what they wish. If I were to be hesitant to mention something I would be so primarily be to protect myself from embarrassment by mentioning them to people who don’t understand rather than to not offend anyone.
So far I would say that, yes, bestiality is something that is politically incorrect for various reasons. It’s probably why we see toilet seats for people to stick their heads under for sale but not canine strap-ons.
And as far as the collar issue is concerned; yes, saying something politically correct about a collar is a way of not offending someone. That’s for the most part the definition of politically correct. However what would something politically incorrect about a collar be? I think people are more afraid to put their deepest feelings down on the table, whichever the topic may be, by virtue of the fact that they are very dear to a person’s heart rather than fear of offending someone. Perhaps you didn’t mean politically correct in the first place.